JP3566599B2 - Image forming apparatus and process cartridge - Google Patents

Description

【０１２９】
【数２】

【０１３０】
このような重合トナーは、単量体組成物を懸濁重合し直接的に製造することができる。例示すると、まず重合性単量体、着色剤、極性樹脂、離型剤、帯電制御剤、重合開始剤、架橋剤などから成る重合性単量体組成物を、水系媒体中へ分散して重合性単量体組成物の粒子を生成させる。そして、この粒子の表面に極性樹脂を局在下させ、粒子中の重合性単量体を重合し、結着樹脂としてトナー粒子形成させる。水系媒体中に水溶性重合開始剤を添加して、トナー粒子表面を処理することにより収率良く生成することができる。
【０１３１】
以下、主な材料を例示する。
【０１３２】
重合性単量体としては、スチレン重合体、スチレン−アクリート共重合体、スチレン−メタクリレート共重合体など、極性樹脂としてはポリエステル樹脂、スチレン共重合体など、着色剤としては、カーボンブラック、ジスアゾ系黄色顔料、キナクリドン系マゼンタ顔料、フタロシアニン系シアン顔料など、離型剤としては、ＤＳＣ吸熱曲線における吸熱メインピーク値が１２０℃以下の低融点物質であるパラフィンワックス、ポリオレフィンワックス、フィッシャートロピッシュワックス、アミドワックス、高級脂肪酸、高級アルコールエステルワックスなど、架橋剤としては、ジビニルベンゼン、カルボン酸エステル、ジビニルアニリンなど、帯電制御剤としては、ニグロシン染料、トリフェニルメタン染料等の正帯電性、含金属サリチル酸化合物、尿素誘導体、アゾ系染料等の負帯電性など、重合開始剤としては、アゾ系や過酸化物系の重合開始剤などである。
【０１３３】
（５）感光体１
本例における像担持体としての感光体１は、感光層の表面に電荷注入層を設けることができる。これにより、帯電性が向上し、像露光時には帯電電荷をより効率的に導電性支持体に逃がす役割をはたし残留電位を低減させることができるので、コントラストの変動が抑えられ長期的に均一な画像が得られる。
【０１３４】
接触帯電と電荷注入層を積層した像担持体と組み合わせることにより注入帯電を達成することができる。注入帯電とは、帯電部材に直流電圧を印加することにより、印加された電荷を効率良く像担持体（被帯電体）に保持形成する帯電方法である。放電を利用した帯電方法に比べ、必要最小限な帯電電位を与える帯電手段であり、従来の直流電圧の放電帯電であるＤＣ帯電と区別される。
【０１３５】
このような注入帯電では、電荷注入層がない従来の感光体に比べ、環境変化や感光体の膜厚変化による帯電性の変動をより小さく抑えることが可能になるので更なる画質の向上が達成され、同時に放電によるオゾンの低減も実現される。
【０１３６】
ところで、注入帯電が行われると放電成分が減少するが、帯電ニップＮでの電荷の授受が促進されるのでトナー極性を反転させる効果は実質的に維持される。
【０１３７】
このような電荷注入層としては、▲１▼．絶縁性の結着樹脂に光透過性でかつ導電性の粒子を適量分散させた樹脂層、▲２▼．半導体などで構成された無機層、を挙げることができるが、その他に、導電性高分子から成る有機層も使用可能である。
【０１３８】
具体的に電荷注入層を説明する。
【０１３９】
１）導電性徴粒子と結着樹脂から成る樹脂層
結着樹脂には、ポリエステル樹脂、ポリカーボネート樹脂、ポリスチレン樹脂、フッ素樹脂、セルロ−ス、塩化ビニル樹脂、ポリウレタン樹脂、アクリル樹脂、エポキシ樹脂、シリコーン樹脂、アルキド樹脂、塩化ビニル−酢酸ビニール共重合体樹脂等の樹脂を用いることができる。
【０１４０】
導電性微粒子としては、銅、アルミニウム、銀、ニッケル等の金属、酸化亜鉛、酸化錫、酸化アンチモン、酸化スズ、酸化チタン、あるいはこれらの固溶体、もしくは融着体等の金属酸化物、ポリアセチレン、ポリチオフェン、ポリピロール等の導電性ポリマー等が使用できるが、感光体の透光性の観点から透明度の高い酸化スズ等の金属酸化物を選択使用することがより好ましい。
【０１４１】
これら導電性微粒子の粒径は、透光性の観点から０．３μｍ以下が好ましく、最適には、０．１μｍ以下である。電荷注入層に含有させる場合、導電性微粒子の含有量は、その粒径にも依存するが、結着樹脂に対し２〜２８０重量％の範囲が好ましい。含有量が２重量％未満では、電荷注入層の抵抗調整が困難となり、また、２８０重量％を越えると結着樹脂の塗膜性が部分的に低下することがある。よって、導電性微粒子の含有量は、結着樹脂に対し２〜２８０重量％の範囲が好ましい。
【０１４２】
導電性微粒子の分散性向上、結着樹脂との接着性、あるいは成膜後の塗膜平滑性の向上を目的として、種々の添加剤を加えることができる。また、分散性の向上に関しては、カップリング剤、あるいはレベリング剤などにより、導電性微粒子の表面改質を行うことは非常に有効である。さらには、分散性向上の点から、結着樹脂として硬化型樹脂を用いることが効果的である。
【０１４３】
硬化型樹脂を電荷注入層に用いる場合には、導電性微粒子を硬化性モノマー又はオリゴマーの溶液中に分散した塗工液を感光層上に塗布、成膜後、熱又は光照射によって該塗膜を硬化させて表面層とする。このような硬化型樹脂としては、例えば、アクリル樹脂、エポキシ樹脂、フェノール樹脂、メラミン樹脂等が挙げられるが、これに限ったわけではなく、塗布成膜後に光又は熱等のエネルギーを与えることにより化学反応を起こし硬化する樹脂であれば使用可能である。
【０１４４】
上記電荷注入層は、結着樹脂、導電性微粒子、及び必要に応じ添加剤の適当な溶液、又は分散溶液を感光体上に塗布乾燥することにより得られ、この膜厚は、好ましくは、０．１〜１０μｍ、最適には、０．５〜５μｍである。
【０１４５】
ここで上記電荷注入層には、滑材粉末を含有させてもよい。感光体と帯電部材との摩擦、または感光体とクリーニング部材との摩擦が低減され、電子写真装置の力的負荷が軽減できる。また、感光体表面の離型性が向上するため、現像剤の付着が防止できる。このような滑材粒子としては、臨界表面張力の低い、フッ素樹脂、シリコーン樹脂、又はポリオレフィン樹脂を用いるのが好ましい。
【０１４６】
特に好ましくは、４フッ化ポリエチレン樹脂である。この場合、滑材粉末の添加量は、好ましくは、電荷注入層重畳に対して、２〜５０重量％、より好ましくは、５〜４０重量％である。２重量％以下では、滑材粉末の量が十分でないため、帯電性の向上効果を十分に発揮できないことがあり、また、５０重量％を越えると、画像の分解能、または感光体の感度が低下する傾向にある。
【０１４７】
２）無機系材料から成る電荷注入層
例えばアモルファスシリコンなどの半導電体を挙げることができる。
【０１４８】
半導体シリコン製の感光体は、下層の感光層に光導電化されたアモルファスシリコンを選択することにより、高周波グロー放電分解によりプラズマ化学気相堆積装置を用いて連続的に作製できる。
【０１４９】
導電性高分子から成る電荷注入層としては、例えばポリピロール、ポリチオフェン、ポリアニリンなどの電子共役性ポリマー、有機ポリシラン類などを挙げることができる。
【０１５０】
電荷注入層の体積抵抗値は、１×１０^８ Ωｃｍ〜１×１０^１５Ωｃｍの範囲に調製することが好ましい。
【０１５１】
電荷注入層の体積抵抗値が１×１０^８ Ωｃｍより小さい場合、静電潜像を保持できずに画像流れが発生し、１×１０^１５Ωｃｍを越えると帯電部材から電荷を十分に受け取ることができず、帯電不良を生じることがある。
【０１５２】
そこで、電荷注入層は、十分な帯電性と画像の再現性を満足するために、体積抵抗値を１×１０^８ Ωｃｍ〜１×１０^１５Ωｃｍの範囲こ調製することが好ましい。
【０１５３】
電荷注入層の体積抵抗は、表面に導電膜を蒸着させたポリエチレンテレフタレート（ＰＥＴ）上に電荷注入層を作成し、これを体積抵抗測定装置（ヒューレットパッカード社製４１４０Ｂ ｐＡＭＡＴＥＲ）にて２３℃、６５％の環境で１００Ｖの電圧を印加し測定した。
【０１５４】
（６）帯電ローラ２１の製造例
［帯電ローラの製造例１］
ＥＰＤＭ １００重量部
酸化亜鉛 ４重量部
アセチレンブラック １０重量部
パラフィンオイル １０重量部
硫黄 １重量部
上記主成分を加硫促進剤、高級脂肪酸と共に水冷させながら２軸混練押出機にて混練した。これを型内で加硫成形し、外径１２ｍｍの弾性ローラを作製した（芯金６ｍｍ）。
【０１５５】
次にメタノール／トルエン混合溶媒に溶解させたメチロール化ナイロン溶液中に弾性ローラを浸漬塗布し、１２０℃で１時間加熱乾燥した。
【０１５６】
ローラ抵抗は３×１０^６ のであった。これを「帯電ローラ１」とする。
【０１５７】
［帯電ローラの製造例２］
帯電ローラの製造例１に於いて、発泡剤（アゾジカルボジアミド）を用いて弾性体を発泡（平均発泡セル径１００μｍ）させ、更に表面を直径１２ｍｍに研磨し発泡ローラとした。
【０１５８】
次に導電性酸化すずスラリー（アンチモンドープ型）をウレタン−アクリル分散液に分散し、アクリル樹脂で増粘させながら粘調な分散液を調製した。この溶液をディッピング法により発泡ローラ表面に塗布し、予備乾燥（５０℃）した後、最終的に１２０℃で１時間加熱乾燥した。
【０１５９】
これを「帯電ローラ２」とする。
【０１６０】
［帯電ローラの製造例３］
ステレン−エチレン−オレフィン共重合体と導電性カーボンブラックから成る樹脂をクロスヘッド押出機を用いて内径１１．５ｍｍ、厚み２５０μｍの導電性シームレスチューブを作製した。
【０１６１】
次にエアーを吹き込みながら帯電ローラの製造例２の発泡ローラに被覆した。
【０１６２】
これを「帯電ローラ３」とする。
【０１６３】
［帯電ローラの製造例４］
トルエンで１重量％に希釈したアミノシラン系カップリング剤（３−アミノプロピルトリエトキシシラン）を「帯電ローラ１」に含侵塗布し、８０℃で１時間乾燥させた後、１２０℃で１時間キュアした。
【０１６４】
このカップリング剤処理品を「帯電ローラ４」とする。
【０１６５】
［帯電ローラの製造例５］
トルエンで１重量％に希釈したチタン系カップリング剤（イソプロピルトリイソステアロイルチタネート）を「帯電ローラ２」に含侵塗布し、１００℃で１時間乾燥させた後、１５０℃で１時間キュアした。
【０１６６】
このカップリング剤処品を「帯電ローラ５」とする。
【０１６７】
［帯電ローラの製造例６］
ＭＥＫで１重量％に希釈したシランカップリング剤（ドデシルトリエトキシシラン）を「帯電ローラ３」にスプレー塗布し、８０℃で１時間乾燥させた後、１２０℃で１時間キュアした。
【０１６８】
このカップリング剤処理品を「帯電ローラ６」とする。
【０１６９】
（７）トナー掻き取り部材（クリーニング部材）２２としての
ブレードとファーブラシの製造例
［ブレードの製造例１］
二液性シリコーンゴムを１５０℃で硬化させシート化した後、２００℃でキュアーして厚み３ｍｍのシリコーンゴム成型体を得た。この成型体を、長さ１５ｍｍ、幅２３０ｍｍに切断し、その長さの内１０ｍｍが固定されるように厚さ０．１ｍｍのステンレス基板に接着してプレードを作製した。
【０１７０】
これを「ブレード１」とする。
【０１７１】
［ブレードの製造例２］
プライマー処理した厚み０．０７ｍｍのステンレス基板に高温硬化型シリコーンゴム（液状シリコーンゴム）を射出成形し、０．７ｍｍのシリコーンゴム弾性層を形成し、更に２００℃条件で加硫した。この一体成形体を切断し、ブレードを作製した。
【０１７２】
これを「ブレード２」とする。
【０１７３】
［ブレードの製造例３］
ＭＤＩ（４，４’ジフェニルメタンジイソシアネート）、エチレングリコールとアジピン酸よりなるポリエステルジオールを主成分とするウレタン原料を窒素雰囲気下で反応させ、ポリエステル平均分子量１７００のプレポリマーを合成した。
【０１７４】
これに硬化剤を加え成形用金型に注入して１５０℃で硬化させた後、脱型し、更に加熱硬化させ、「ブレード１」と同様に切断してブレードを作製した。
【０１７５】
これを「ブレード３」とする。
【０１７６】
［ブレードの製造例４］
Ｔｉ系カップリング剤（イソプロピルトリイソステアロイルチタネート）をトルエンで希釈し１重量％とした。この溶液中に「ブレード１」を含侵させ、取り出した後、８０℃で加熱乾燥させ、更に１５０℃で１時間キュアした。
【０１７７】
これを「ブレード４」とする。
【０１７８】
［ブレードの製造例５］
アミノシランカップリング剤（３−アミノプロピルトリエトキシシラン）をＭＥＫで希釈し１重量％とした。この溶液中に「ブレード３」を含侵させカップリング処理を行った。
【０１７９】
これを「ブレード５」とする。
【０１８０】
［ファーブラシの製造例１］（参考例）
導電性カーボンを練り込んだレーヨン繊維（平均繊維径１５μｍ）を基布に対しＷ型に織り、繊維密度２０万本／inch² 、パイル長５ｍｍのブラシ織物を作製した。これを直径６ｍｍのステンレス製芯金に接着剤を介してスパイラル状に巻き付け、ローラ形状のファーブラシを作製した。
【０１８１】
これを「ファーブラシ１」とする。
【０１８２】
［ファーブラシの製造例２］（参考例）
平均繊維径１３μｍのＰＥＴ繊維を基布に対しＷ字型に織り、繊維密度２０万本／inch² 、パイル長５ｍｍ、幅１０ｍｍのブラシ織物を作製した。
【０１８３】
このブラシ織物にＴｉ系カップリング剤（イソプロピルトリイソステアロイルチタネート）をトルエンで希釈し１重量％とした溶液を噴霧し含侵させた後、最終的に１２０℃で１時間キュアした。
【０１８４】
次にＳＵＳ製芯金に接着剤を介してスパイラル状に巻き付けローラ形状のファーブラシを作製した。
【０１８５】
これを「ファーブラシ２」とする。
【０１８６】
（８）トナー及び現像剤の製造例
［トナーの製造例１］
ポリエステル樹脂 １００質量部
合金属アゾ染料 ２．５質量部
低分子量ポリプロピレン ４質量部
カーボンブラック ４質量部
上記材料を乾式混合した後に、１５０℃に設定した２軸混練押出機にて混練した。得られた混練物を空冷し、気流式粉砕機により微粉砕した後に風力分級して粒度分布の調整されたトナー組成物を得た。
【０１８７】
このトナー組成物に、疎水化処理された酸化チタン１．５重量％を外添して、重量平均粒径７．０μｍのトナーを作製した。
【０１８８】
［トナーの製造例２］
ステレン ９０質量部
ｎ−ブチルアクリレート １０質量部
低分子量ポリプロピレン ５質量部
カーボンブラック ５質量部
含金属アゾ染料 ２質量部
アゾ系開始剤 ５質量部
を分散混合し、上記溶液を燐酸カルシウム５質量部を分散した純水５００質量部に加えホモミキサーにより分散し、最終的に７５℃で、１０時間重合し得られた重合体をろ過し、洗浄を行った後に、乾燥分級し、トナー組成物を得た。
【０１８９】
上記トナー組成物に、疎水化処理された酸化チタン２重量％を外添し、重量平均径６．１μｍのトナーを作成した。
【０１９０】
得られたトナーは、重合法により形成されており、電子顕微鏡にて観察したところ、球状を示している。形状係数は、ＳＦ−１は１２０、ＳＦ−２は１１０であった。
【０１９１】
［現像剤製造例１］
平均径６０μｍのニッケル亜鉛フェライトにシリコーン樹脂をコートした現像キャリア（１００質量部）に、トナー製造例１のトナーを７質量部を混合した。
【０１９２】
これを「現像剤１」とする。
【０１９３】
［現像剤製造例２］
平均径６０μｍのニッケル亜鉛フェライトにアクリル変性シリコーン樹脂をコートした現像キャリア（１００質量部）に、トナー製造例２のトナーを７質量部を混合した。
【０１９４】
これを「現像剤２」とする。
【０１９５】
（９）感光体の製造例
［感光体の製造例１］
φ３０ｍｍのアルミニウムシリンダー上に感光層を積層しＯＰＣ感光体１を作製した。
【０１９６】
積層した層は、アルミニウムシリンダーから順に次の第１層〜第４層である。
【０１９７】
第１層は下引き層である。アルミニウムシリンダーの欠陥等をならすため、またレーザ露光の反射によるモアレ発生を防止するために導電性を有する膜厚３０μｍの薄層を設けた。
【０１９８】
第２層は正電荷注入防止層である。アルミニウムシリンダー側から注入された正電荷が感光体表面に帯電された負電荷を打ち消すことを防止する目的で、１０^６ Ωｃｍオーダーに抵抗調整したアミラン樹脂とメトキシメチル化ナイロンから成る層を約１μｍ形成した。
【０１９９】
第３層は電荷発生層である。ジスアゾ系顔料を分散した厚さ約０．４μｍの樹脂層であり、レーザ露光により正負の電荷対を発生させることができる。
【０２００】
第４層は電荷輸送層である。ポリカーボネート樹脂にヒドラゾンを分散し、Ｐ型半導体層（約２５μｍ）を形成した。この層は、電荷発生層で発生した正電荷を感光体表面に輸送する機能を有し、感光体表面に帯電された負電荷は、この層を移動することはできない。
【０２０１】
これを「感光体１」とする。
【０２０２】
［感光体製造例２］
前記感光体製造例１に於て、［感光体１］の表面に第５層目としての電荷注入層を設けた。
【０２０３】
電荷注入層は、光硬化性アクリル樹脂に酸化すずを分散した導電性を有する樹脂層である。
【０２０４】
用いた酸化すずは、アンチモンをドーピングして導電化した粒径約０．０３μｍの超微粒子であり、結着樹脂である光硬化性アクリル樹脂に対して１３０重量％分散した。抵抗は４×１０^１３Ωｃｍである。
【０２０５】
電荷注入層には、表面滑り性向上の目的で、４フッ化エチレン樹脂粒子を３０重量％分散した。
【０２０６】
これを「感光体２」とする。
【０２０７】
［感光体の製造例３］
鏡面加工を施したφ３０ｍｍのアルミニウムシリンダーにグロー放電法を用いて、阻止層、光導電層、表面層からなるアモルファスシリコン感光体を作製した。
【０２０８】
先ず、反応室を約５×１０^−３Ｐａに排気してから、２５０℃に調温されたアルミニウムシリンダー表面に各種ガス（ＳｉＨ_４ 、Ｂ_２ Ｈ_６ 、ＮＯ、Ｈ_２ ）をフロー式で反応室に送り込み、２０Ｐａ程度の内圧に達したところでグロー放電を生起させ、約４μｍの阻止層を形成した。
【０２０９】
次に同様な方法で、ＳｉＨ_４ 、Ｈ_２ ガスを使用し、約５０Ｐａの内圧条件下で２５μｍの光導電層を形成した。
【０２１０】
更に、ＳｉＨ_４ 、ＣＨ_４ 、Ｈ_２ ガスを使用し、約６０Ｐａの内圧条件下でグロー放電させて、膜厚０．４μｍのＳｉとＣからなる表面層を形成し、アモルファスシリコン感光体を作製した。
【０２１１】
これを「感光体３」とする。
【０２１２】
（１０）実施例と比較例
以下、実施例と比較例により本発明の効果を示す。
【０２１３】
まず、評価の為に画像形成装置としてレーザービームを用いたデジタル複写機（キヤノン製：ＧＰ５５）を改造して使用した。
【０２１４】
ＧＰ５５は、基本的に、コロナ帯電、１成分ジャンピング現像、コロナ帯電、ブレード式のクリーニング容器、露光手段を備え、プロセススピード１５０ｍｍ／ｓの反転現像方式のデジタル複写機であるが、以下のように改造して図１のようなクリーナーレス検討機とした。
【０２１５】
１）現像：２成分現像装置（反転現像）４を使用可能にした。バイアスは、−５００Ｖ／１０００Ｖｐｐ（３ｋＨｚ）の矩形波を重量した。
【０２１６】
２）帯電：帯電部材として帯電ローラ２１を用いた接触帯電装置２であり、帯電ローラ２１にクリーニング部材（トナー掻き取り部材）２２を当接させた。帯電ローラ２１には感光体１に対し対向回転できるように外部駆動モータを接続し、周速差を１１０％にした。更に、ローラタイプのクリーニング部材の為に外部駆動を設け帯電ローラに対し対向回転さるようにもした。
【０２１７】
３）帯電バイアス
：外部電源により、ＤＣ帯電として−１３００Ｖ、ＡＣ帯電として−７００Ｖ／１５００Ｖｐｐ（８００Ｈｚ）、注入帯電として弱ＤＣ電圧（−１０００Ｖ）をそれぞれ印加した。
【０２１８】
４）クリーニング容器：クリーニングブレードおよび廃トナー容器を取り去りクリーナレスとした。
【０２１９】
次に評価は、６％文字原稿をＡ４横送りで１０ｋ枚連続画出し耐久を行い、ゴースト、帯電不良により発生する画像カブリを反射濃度計で計測した。耐久環境は、２３℃／相対湿度６０％（Ｎ／Ｎ環境）、２３℃／相対湿度１０％（Ｎ／Ｌ環境）、１５℃／相対湿度１０％（Ｌ／Ｌ環境）である。
【０２２０】
本評価では、ＪＩＳ Ｚ８７２２（０度−４５度法）に基づいた反射濃度計（東京電色技術センター、ＴＣ−６ＭＣ）を用い画出し前後の差（％）を算出しカブリ濃度とした。
【０２２１】
評価レベルは、表１の通りであり、画質として５％未満を実用上問題なしと判断する。
【０２２２】
［実施例１］
カップリング剤で表面処理した「帯電ローラ６」に「ブレード１」を対向当接した接触帯電装置を前記のデジタル複写機に搭載し、Ｎ／Ｎ、Ｎ／Ｌ、Ｌ／Ｌの３環境に於いて、ＤＣ帯電による１０ｋ枚の画出し耐久を行い、耐久前後のカブリを評価した。
【０２２３】
ここで、現像剤は重合トナーからなる「現像剤２」、感光体は電荷注入層を有する「感光体２」を使用した。
【０２２４】
表１の評価レベルに基づいた結果を表２に整理した。
【０２２５】
本実施例では、カップリング剤処理により転写残トナーの回収が良好に行われ、帯電が厳しいＬ／Ｌ環境に於いてもカブリ１％以下であった。その結果、高画質が達成された。
【０２２６】
［実施例２〜４］
表２に示す各部材を用いて実施例１と同様な評価を行った。
【０２２７】
ここで、帯電ローラの回転に対し、「ブレード４」は対向当接、「ファーブラシ１」および「ファーブラシ２」は同じ周速で対向回転させた。なお、「ファーブラシ１」および「ファーブラシ２」を用いた実施例３と４は参考例である。
【０２２８】
その結果、帯電ローラ２１のクリーニング部材（トナー掻き取り部材）２２として、カップリング剤で表面処理したファーブラシを用いることにより（実施例３、４）良好な画質が得られ、更に、ブレードを用いた実施例２では、実施例１と同様にＬ／Ｌ環境に於いてもカブリ１％以下の良好な画質が得られた。
【０２２９】
［実施例５〜７］
表２に示す各部材を用いて実施例１と同様な評価を行ったところ、それぞれの帯電条件でカブリ１％以下の良好な画質が得られた。ここで、実施例６の交流成分は、１．１ｋＶｐｐ、１．０ｋＨｚとした。
【０２３０】
［実施例８］
カップリング剤で表面処理した「ブレード５」を帯電ローラ２１に図４のように面接触させ約１ｍｍ幅のニップを確保した状態で実施例１と同様な評価を行った。この実施例８も参考例である。
【０２３１】
その結果、実施例１と同レベルの高画質が得られた。
【０２３２】
［実施例９〜１１］
表２に示す各部材を用いてＮ／ＮおよびＮ／Ｌの２環境で実施例１と同様な評価を行った。なお、「ファーブラシ１」を用いた実施例１０は参考例である。
【０２３３】
その結果、Ｎ／Ｌ環境でも十分な画質が得られた。
【０２３４】
［実施例１２〜１５］
表２に示すカップリング処理部材および「感光体１」を用いてＮ／ＮおよびＮ／Ｌの２環境で実施例１と同様な評価を行った。なお、「ファーブラシ１」および「ファーブラシ２」を用いた実施例１４と１５は参考例である。
【０２３５】
ここで、「ブレード１」、「ブレード４」は対向当接、「ファーブラシ１」、「ファーブラシ２」は対向回転させた。
【０２３６】
その結果、Ｎ／Ｎ環境で高画質が達成され、更にブレードを採用した実施例１２、１３はＮ／Ｌ環境に於いてもカブリが１〜３％と抑えられた良好な画質が得られた。
【０２３７】
［実施例１６］
「帯電ローラ４」に「ブレード２」を対向当接させ（表２）、ＡＣ帯電によるＮ／Ｎ環境での耐久を行ったところ、カブリ１％以下の高画質が得られた。
【０２３８】
［実施例１７、１８］
表２に示す各部材を用いて実施例１と同様な方法でＮ／Ｎ環境で画出し耐久を行った。その結果、カブリが１〜３％に抑えられた良好な画像が得られた。なお、「ファーブラシ１」を用いた実施例１８は参考例である。
【０２３９】
［実施例１９〜２５］
表２に示す各部材を用いて実施例１と同様な方法でＮ／Ｎ環境で画出し耐久を行った。なお、「ファーブラシ１」および「ファーブラシ２」を用いた実施例１９は参考例である。
【０２４０】
その結果、粉砕トナーおよび「感光体１」を組み合わせた系（実施例２４、２５）では、カブリは実用上問題のない３〜５％のレベルであり、更にクリーニング部材（トナー掻き取り部材）をカップリング処理することにより（実施例１９〜２３）、カブリは２％に低減し画像の向上が認められた。
【０２４１】
［比較例１］
「帯電ローラ１」を「感光体１」に当接し「現像剤１」を用いて実施例１と同様な評価をＮ／Ｎ環境で行った。帯電ローラは、感光体に従動回転し、帯電はＤＣ帯電とした。
【０２４２】
その結果、耐久初期からカブリが発生し画質は低下した。
【０２４３】
［比較例２］
「ファーブラシ１」を用いて実施例１と同様な評価をＮ／Ｎ環境で行った。帯電部材として外部駆動により対向回転（周速差１３０％）させた。ここで、「ファーブラシ１」は、空回転評価で画像形成に必要な初期帯電電位が得られることを確認している。
【０２４４】
その結果、耐久初期からカブリが発生し画質は低下した。
【０２４５】
［比較例３］
比較例１に於いてＡＣ帯電で同様な評価を行ったところ、やはり耐久初期からカブリが発生し画質は低下した。
【０２４６】
【表１】

【０２４７】
【表２】

【０２４８】
（１１）その他
１）本発明において画像形成装置には像担持体上の転写残トナーを捕集するクリーナー装置を設けてもよく、この場合は転写手段５と帯電手段２の間に設置することが好ましい。そのクリーナー装置をプロセスカートリッジに具備させることもできる。
【０２４９】
２）接触帯電部材としての帯電ローラ２１はフェルトや布などの材質のものも使用可能である。それら各種材質材を組み合わせ、積層して、より適切な弾性と導電性を得ることもできる。
【０２５０】
３）帯電バイアスや現像バイアスに交流（交番）電圧を重畳する場合の交流電圧の波形としては、正弦波、矩形波、三角波等適宜使用可能である。また直流電源を周期的にオン／オフすることによって形成された矩形波であってもよい。このように交流電圧の波形としては周期的にその電圧値が変化するようなバイアスが使用できる。
【０２５１】
４）静電潜像形成のための画像露光手段としては、実施形態例のようにデジタル的な潜像を形成するレーザー走査露光手段に限定されるものではなく、通常のアナログ的な画像露光手段であってもよい。ＬＥＤなどの発光素子アレイや、蛍光灯等の発光光源と液晶シャッターアレイとの組み合わせ等の露光手段であってもよく、画像情報に対応した静電潜像を形成できるものであればよい。
【０２５２】
５）像担持体は静電記録誘電体等であってもよい。この場合は該誘電体面を所定の極性・電位に一様に一次帯電した後、除電針ヘッド、電子銃等の除電処理手段で選択的に除電して目的の静電潜像を書き込み形成する。
【０２５３】
６）一般に静電潜像の現像手段は、非磁性トナーについてはブレード等で現像部材上にコーティングし、磁性トナーは磁気力によってコーティングして搬送して像担持体に対して非接触状態で現像する方法（１成分非接触現像）と、上記のようにしてコーティングしたトナーを像担持体に対して接触状態で現像する方法（１成分接触現像）と、トナー粒子に対して磁性のキャリアを混合したものを現像剤として用いて磁気力によって搬送して像担持体に対して接触状態で現像する方法（２成分接触現像）と、上記の２成分現像剤を非接触状態にして現像する方法（２成分非接触現像）との４種類に大別される。
【０２５４】
画像の高画質化や高安定性の面から２成分接触現像法が多く用いられている。また現像剤を像担持体に接触させて現像する１成分接触現像法や２成分接触現像法がより現像時の同時トナー回収性を高めるのに効果があり、好ましい。
【０２５５】
また、現像剤中のトナー粒子として重合トナーを用いた場合には、上記の１成分接触現像法や２成分接触現像法はもちろん１成分非接触現像法や２成分非接触現像法などの現像方法においても充分な回収効果が得られる。
【０２５６】
７）転写手段は転写ローラ５に限られず、ベルト転写装置や転写コロナ帯電器等であってもよい。更には、転写ドラムや転写ベルトなどの中間転写体を用いて、単色画像形成ばかりでなく、多重転写により多色、フルカラー画像を形成することもできる。
【０２５７】
【発明の効果】
以上説明したように本発明では、回転する像担持体と、該像担持体の面を帯電する帯電手段と、像担持体の帯電面に静電潜像を形成する潜像形成手段と、その静電潜像をトナー像として現像する現像手段と、そのトナー像を記録媒体に転写する転写手段を備えた画像形成装置、およびこのような画像形成装置に搭載されるプロセスカートリッジにおいて、転写残トナーの極性を制御することにより、帯電手段の接触帯電部材へのトナー蓄積を防止する共に、現像手段でのトナー回収性を向上させた。その結果、長期的に均一な帯電が持続し、高画質が達成された。
【図面の簡単な説明】
【図１】一実施形態例の画像形成装置の概略構成図
【図２】帯電ローラの層構成模型図
【図３】トナー掻き取り部材としてのブレードを帯電ローラに対して対向当接して配設する場合の要領説明図
【図４】トナー掻き取り部材としてのブレードを帯電ローラに対して面接触で配設した状態を示した図
【符号の説明】
１ 感光体
２ 接触帯電装置
２１ 帯電ローラ
２２ 帯電ローラからのトナー掻き取り部材（クリーニング部材）とし
てのブレード
３ 潜像形成手段（レーザースキャナー）
４ 現像装置
５ 転写ローラ
６ 定着装置
Ｐ 転写材（普通紙など）
Ｓ１〜Ｓ３ バイアス印加電源[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus and a process cartridge.
[0002]
[Prior art]
For example, in a transfer type electrophotographic apparatus, the cleaning step of removing the transfer residual toner remaining on the photoreceptor (image carrier) after the transfer from the photoreceptor surface is performed by pressing the cleaning member against the photoreceptor to block the transfer residual toner and waste toner. This is a step of scraping and collecting into a container, and a blade-type cleaning member is used. Since such a cleaning member is brought into direct contact with the photoreceptor, it is excellent in collecting residual toner after transfer.
[0003]
However, when the cleaning member is deteriorated due to the effects of long-term durability or fine powder, the toner remaining after transfer from the cleaning member may adhere to the charging member and the uniform charging property may be reduced. Therefore, improvement of the cleaning member is desired. ing.
[0004]
In addition, it is pointed out that the cleaning member wears (shortens the life) of the photoconductor, that the waste toner needs to be treated, and that the apparatus becomes inevitably large due to the provision of the cleaning container. .
[0005]
Therefore, from the viewpoints of ecology, photoreceptor life, miniaturization of the apparatus, and effective use of toner, a simultaneous cleaning system (cleaner-less) has been proposed as a system without waste toner.
[0006]
This eliminates the cleaner and removes the transfer residual toner on the photoreceptor after transfer from the photoreceptor by simultaneous cleaning with a developing device (developing device), and collects and reuses the toner in the developing device. An image forming apparatus.
[0007]
In the simultaneous cleaning with development, the toner remaining on the photoreceptor after transfer is collected by a fogging bias (fogging potential difference Vback, which is a potential difference between a DC voltage applied to a developing device and a surface potential of the photoreceptor) at the time of subsequent development. How to According to this method, the transfer residual toner is collected in the developing device and reused after the next step, so that waste toner can be eliminated and maintenance can be facilitated. In addition, the cleaner-less system has a great advantage in terms of space, and can further reduce the size of the image forming apparatus.
[0008]
Japanese Patent Application Laid-Open No. Hei 5-346751 proposes an apparatus for simultaneous development and cleaning using a fur brush charger as a contact charging member as a charging means for a photoconductor. The transfer residual toner is scraped off once from the photoreceptor by the rotation of the fur brush, and adheres to the photoreceptor again. An AC superimposed bias is applied to the fur brush charger to increase the charging efficiency. In this case, sufficient toner ejection cannot be obtained only by the rotational force of the fur brush, and the AC superimposed bias reduces the electrostatic ejection of toner (adhesion to the photoreceptor). It becomes difficult to prevent.
[0009]
JP-A-6-149020 discloses a technique in which a blade is brought into contact with a charging roller to physically scrape off attached toner. The blade is located downstream of the charging roller that rotates in the forward direction with respect to the rotation of the photoconductor. Since the toner scraped off by the blade falls to the downstream side of the photoreceptor, it does not pass through the charging nip, so that the toner is prevented from staying at the falling point. However, there is a limit in the physical scraping of the toner and the collecting property of the dropped toner, and the cleaning property of the charging roller is deteriorated when the toner is used for a long time or when the transfer residual toner frequently occurs.
[0010]
JP-A-6-342237 also discloses a technique in which a cleaning blade is mounted on a charging roller. This is to prevent the toner from adhering to the charging roller by charging the surface of the charging roller to the same polarity as the developing toner by friction between the charging roller and the cleaning blade. However, when the polarity of the transfer residual toner becomes non-uniform due to the influence of the transfer bias or the like, a sufficient effect cannot be obtained.
[0011]
[Problems to be solved by the invention]
In the simultaneous-developing cleaning system, the transfer residual toner passes through the charging member, and is collected and reused by the developing device. However, since the polarity of the transfer residual toner includes both the developing polarity and the reverse polarity, the transfer residual toner inverted to the reverse polarity is electrostatically attached to the charging member. When the toner adheres to the charging member, charging failure due to toner contamination occurs, or the toner collecting property in the developing device is reduced. Further, when the transfer residual toner having the opposite polarity is mixed into the developing device, fogging may occur.
[0012]
In the method in which the toner adhered to the charging member is removed by the cleaning member, the polarity of the toner is not controlled, so that the toner collecting property in the developing device is insufficient. Also, the method of applying a reverse bias to the charging member during non-image formation does not have a sufficient effect of discharging the adhered toner to the photoreceptor side. Low.
[0013]
Therefore, it is necessary to control the polarity of the transfer residual toner.
[0014]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus that realizes high image quality by controlling the polarity of a transfer residual toner or a toner that has slipped through a cleaner device and enabling toner collection in a developing device, and an image forming apparatus. To provide a process cartridge that performs
[0015]
[Means for Solving the Problems]
The present invention is an image forming apparatus and a process cartridge having the following configurations.
[0016]
(1) A rotating image carrier, charging means for charging the surface of the image carrier, latent image forming means for forming an electrostatic latent image on the charged surface of the image carrier, and toner An image forming apparatus including a developing unit that develops an image and a transfer unit that transfers the toner image to a recording medium;
The charging unit rotates in a reverse direction with respect to the image carrier at a contact portion with the image carrier, and applies a voltage to charge the surface of the image carrier.rollerAnd the chargingThe edge part counter-contacts the roller and the charging rollerScraping toner onto the image carrier upstream of the contact portion with respect to the rotation direction of the image carrier;Blade shapedAn image forming apparatus comprising: a toner scraping member; and at least the charging member has a polarity control agent for controlling toner charge to have the same polarity as the charging polarity of the image carrier.
[0018]
(2)The surface of the toner scraping member has a polarity control agent for controlling the toner charge to the same polarity as the charging polarity of the image carrier.(1)An image forming apparatus according to claim 1.
[0020]
(3)The toner is a spherical toner produced using a polymerization method.(1) or (2)An image forming apparatus according to claim 1.
[0021]
(4)The image bearing member is a photosensitive member having a photosensitive layer on a conductive substrate.Any one of (1) to (3)An image forming apparatus according to claim 1.
[0022]
(5)The image bearing member is a photosensitive member having at least a photosensitive layer and a charge injection layer on a conductive substrate.Any one of (1) to (4)An image forming apparatus according to claim 1.
[0023]
(6)The charge injection layer is a resin layer in which a metal oxide is dispersed.(5)An image forming apparatus according to claim 1.
[0024]
(7)The charge injection layer is an inorganic semiconductor layer.(5)An image forming apparatus according to claim 1.
[0025]
(8)The developing means also serves as a cleaning means for collecting a transfer residual toner remaining on the image carrier after transferring the toner image to a recording medium.Any one of (1) to (7)An image forming apparatus according to claim 1.
[0026]
(9)At least a rotating image carrier, and a charging unit for charging a surface of the image carrier, a process cartridge detachable from the image forming apparatus main body.
The charging unit rotates in a reverse direction with respect to the image carrier at a contact portion with the image carrier, and applies a voltage to charge the surface of the image carrier.rollerAnd the chargingThe edge part counter-contacts the roller and the charging rollerScraping toner onto the image carrier upstream of the contact portion with respect to the rotation direction of the image carrier;Blade shapedA process cartridge comprising: a toner scraping member; and at least the charging member has a polarity control agent for controlling the toner charge to the same polarity as the charging polarity of the image carrier.
[0027]
(10)A developing unit for developing the electrostatic latent image formed on the charged surface of the image carrier as a toner image;(9)The process cartridge according to 1.
[0029]
(11)The surface of the toner scraping member has a polarity control agent for controlling the toner charge to the same polarity as the charging polarity of the image carrier.(9) or (10)The process cartridge according to 1.
[0031]
(12)The toner is a spherical toner produced using a polymerization method.Any one of (9) to (11)The process cartridge according to 1.
[0032]
(13)The image bearing member is a photosensitive member having at least a photosensitive layer on a conductive substrate.Any one of (9) to (12)The process cartridge according to 1.
[0033]
(14)The image bearing member is a photosensitive member having at least a photosensitive layer and a charge injection layer on a conductive substrate.Any one of (9) to (13)The process cartridge according to 1.
[0034]
(15)The charge injection layer is a resin in which a metal oxide is dispersed.(14)The process cartridge according to 1.
[0035]
(16)The charge injection layer is an inorganic semiconductor.(14)The process cartridge according to 1.
[0036]
<Operation>
That is, as the image carrier rotates, the image carrier and the charging memberIs a charging rollerThe transfer residual toner carried to the contact portion (charging nip) or a part of the toner passing through the cleaner device passes through the charging nip, and is collected by the developing means using a potential difference between the image carrier and the developing means. Other transfer residual tonerCharging rollerAdheres to The polarity of the toner carried to the charging nip contains reversal components due to the influence of the transfer bias, etc.Charging rollerTend to be easily attracted electrostatically.
[0037]
In the present invention, the attached toner is provided with a polarity controlling agent.Charging roller, And is controlled to the charging polarity of the image carrier. This effect isA charging roller that rotates in a reverse direction at a contact portion of the image carrier with respect to the image carrier and applies a voltage to charge the surface of the image carrier;ElectrificationAn edge portion of the charging roller is counter-contacted with the roller, and the toner on the charging roller is scraped onto the image carrier upstream from the contact portion in the image carrier rotation direction.The toner that is most efficiently performed at the contact portion of the scraping member and whose polarity is controlled is scraped off at the contact portion and moves onto the image carrier. Since the toner whose polarity has become non-uniform is recharged to the original negative electrode name,Charging rollerIs released from electrostatic binding (adhesive force), and the scraping member scrapes the toner efficiently. as a result,Charging rollerTo prevent continuous toner adhesion and long-term toner adhesion.
[0038]
Also, the toner that has not been scraped offCharging rollerAfter moving to the charging nip according to the rotation ofCharging rollerIt is discharged to the image carrier using the potential difference between the image carrier and the image carrier.
[0039]
In any case, the polarity-controlled toner passes through the charging nip, but in the present invention, the toner polarity is changed to the image carrier charging polarity, that is,Charging rollerAfter passing through the charging nip after controlling to the same polarity asCharging rollerElectrostatic adhesion of toner to theCharging rollerIs also prevented from being deposited on the toner.
[0040]
In the charging nip, charge of the same polarity is suppliedCharging rollerThereby, the toner polarity is controlled more uniformly. The polarity-controlled toner moves to the developing unit according to the rotation of the image carrier, is collected by the developing unit, and is reused.
[0041]
Charging rollerBy releasing the electrostatic binding force using a charge control agent, the scraping performance is dramatically improved, and the long-termCharging rollerSince contamination can be prevented, uniform charging is possible, and as an effect thereof, high image quality can be achieved even in a simultaneous development cleaning system that does not have a cleaner device for collecting transfer residual toner.
[0042]
Further, due to the dual action of the polarity control agent and the discharge near the charging nip, more efficient toner polarity control is performed.
[0043]
Since the polarity is controlled, the collection by the developing means is performed efficiently, thereby preventing ghost images, and in particular, maintaining high image quality for a long period of time even in a high-speed machine with a high process speed or a sudden environmental change. You.
[0044]
A polarity controlling agent capable of controlling the polarity of the toner to the same polarity as the charging polarity of the image carrier can be applied to the toner scraping member. This is more effective especially when a large amount of transfer residual toner is continuously generated.
[0045]
BEST MODE FOR CARRYING OUT THE INVENTION
(1) Example of image forming apparatus
FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus of this embodiment is a laser beam printer (digital copying machine) using a transfer type electrophotographic process, a contact charging system, a reversal developing system, a simultaneous development cleaning system, and a process cartridge system.
[0046]
Reference numeral 1 denotes a drum-type electrophotographic photosensitive member as an image carrier, which is rotationally driven at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow.
[0047]
The photoreceptor has at least a photosensitive layer formed on a conductive support, and such a photosensitive layer is formed by laminating a charge generation layer and a charge transport layer, and the charge generation material and the charge transport material constituting each layer. May be a single-layer type. The charge transport layer has a thickness of 5 to 40 μm, and the charge generation layer has a thickness of 0.05 to 5 μm. Examples of photosensitive layer materials include organic materials such as phthalocyanine pigments and azo pigments, and silicon. Examples include inorganic materials such as compounds. As the conductive support of the photoreceptor, a metal such as aluminum, nickel, stainless steel, steel, or the like, plastic or glass having a conductive film, conductive paper, or the like is used.
[0048]
Reference numeral 2 denotes charging means for uniformly charging the surface of the photoconductor 1 to a predetermined polarity and potential. This example is a contact charging device using a charging roller (conductive / elastic roller) as a charging member.
[0049]
Reference numeral 21 denotes a charging roller as a charging member, which is pressed against the photoconductor 1 by an urging member 23 with a predetermined pressing force. The contact portion between the charging roller 21 and the photoconductor is a charging nip N. A polarity controlling agent is applied to the charging roller 21 as described later.
[0050]
The charging roller 21 is rotated to face the photoconductor 1. That is, the photoconductor 1 is rotationally driven at a predetermined peripheral speed in the direction opposite to the rotation direction of the photoconductor 1 in the charging nip N. The rotation speed can be adjusted by an external drive.
[0051]
S1 is a charging bias power supply. A predetermined charging bias is applied to the charging roller 21 from the power supply S1, and the surface of the photoconductor 1 is contact-charged to a predetermined polarity and potential.
[0052]
As the charging bias applied to the charging roller 21, a DC bias or a bias obtained by superimposing an alternating current on a direct current is employed. The frequency and peak-to-peak (pp) of the AC bias can be arbitrarily set.
[0053]
Reference numeral 22 denotes a toner scraping member (also referred to as a cleaning member) that scrapes off extraneous matter such as toner from the surface of the charging roller 21. In this embodiment, the blade is in contact with the charging roller 2. The blade 22 as a cleaning member has its leading edge attached to the side surface of the charging roller downstream of the charging nip N, which is the contact portion between the charging roller 21 and the photosensitive member 1 (the charging downstream side). It is arranged in contact with the counter in the direction of rotation. Deposits such as toner adhering to the surface of the charging roller 21 are caused by the rotation of the charging roller 21 by the blade 22 on the photosensitive member on the charging downstream side of the charging nip N., That is, the position on the photoconductor upstream of the photoconductor rotation directionIs scraped off.
[0054]
Reference numeral 3 denotes a laser scanner as a latent image forming unit. This laser scanner outputs a laser beam whose intensity is modulated in accordance with a time-series electric digital pixel signal of target image information, and scans and exposes the uniformly charged surface of the rotating photoreceptor 1 with the laser beam. By this scanning exposure L, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotating photoconductor 1.
[0055]
Reference numeral 4 denotes a contact type or proximity type (non-contact type) toner developing device as a developing unit. In this example, it is a reversal developing device. Reference numeral 41 denotes a rotating developing roller (developing sleeve) as a developing member, which carries a developer on the developing roller and is brought into contact with or close to the photoconductor 1. The contact portion or the approach portion is the developing site D. S2 is a developing bias power source, and a predetermined developing bias is applied to the developing roller 41, and the electrostatic latent image formed on the surface of the photoconductor 1 is reversely developed as a toner image (to the same polarity as the photoconductor charging polarity). (Development of an electrostatic latent image by the electrostatically processed toner).
[0056]
Reference numeral 5 denotes a toner image transfer unit. In this embodiment, a transfer roller having a medium resistance is used as a contact transfer unit, and a transfer nip T is formed by pressing the photosensitive member 1 at a predetermined pressure. A transfer material P as a recording medium is supplied to the transfer nip T from a paper supply unit (not shown) at a predetermined timing, and a transfer bias power source S3 supplies a predetermined transfer bias (a bias having a polarity opposite to that of the toner) to the transfer roller 5. Is applied for a predetermined period at a predetermined timing, so that the toner image on the photoconductor 1 side is sequentially transferred to the surface of the transfer material P fed to the transfer nip portion T. That is, the transfer material P introduced into the transfer nip T is nipped and conveyed by the transfer nip T, and the toner image formed and carried on the surface of the photoreceptor 1 is sequentially transferred to the surface thereof by electrostatic force and pressing force. Will be done.
[0057]
Reference numeral 6 denotes a fixing device such as a heat fixing method. The transfer material P that has exited the transfer nip T is separated from the surface of the rotating photoreceptor 1 and is introduced into the fixing device 6, where the toner image is fixed and discharged out of the device as an image formed product (print, copy). .
[0058]
The printer of this embodiment is cleaner-less, and the transfer residual toner remaining on the surface of the photoconductor 1 after the transfer of the toner image onto the transfer material P passes through the charging nip N with the continuous rotation of the photoconductor 1, and the developing portion D At the same time, the toner is collected by the developing simultaneous cleaning by the developing device 4 and reused (toner recycling process).
[0059]
The printer according to the present embodiment is a process cartridge PC in which three process devices of a photoconductor 1, a charging device 2, and a developing device 4 are collectively attached to and detached from a printer main body. Reference numeral 10 denotes a process cartridge attaching / detaching guide / holding member on the printer main body side. The process cartridge PC is mechanically and electrically connected to the printer main body by being mounted in the printer main body in a predetermined manner.
[0060]
In the present invention, the process cartridge is configured such that at least the image carrier and the charging unit are integrally formed into a cartridge, and the cartridge is detachably mountable to the main body of the image forming apparatus. One or more of other process devices such as a developing unit and a cleaning unit may be added to form a cartridge integrally, and this cartridge may be made detachable from the image forming apparatus main body.
[0061]
In the reversal type image forming, when the charged polarity of the photoconductor is negative, similarly, the negatively charged toner forms an image on the photoconductor.
[0062]
The toner image is electrostatically transferred to the transfer material P by the transfer member 5 that applies a reverse-polarity bias located on the rear surface of the transfer material in the transfer nip T, but a part of the toner image is transferred onto the photoconductor 1 as transfer residual toner. Remains.
[0063]
A part of the transfer residual toner passes through the charging nip N formed by the charging roller 21 and the photoconductor 1 according to the rotation of the photoconductor, and is collected in the developing device 4 by utilizing a potential difference between the photoconductor and the developing device. Transfer residual toner adheres to the charging roller 21. The polarity of the transfer residual toner includes a reversal component (positive polarity) under the influence of the transfer bias, and tends to be easily electrostatically attracted to the charging roller 21 that supplies the negative charge.
[0064]
The attached toner is controlled to the photoconductor charging polarity by contact with the charging roller 21 provided with the polarity control agent. This operation is most efficiently performed at the contact portion between the charging roller 21 and the toner scraping member 22, and the toner whose polarity is controlled is scraped off at the contact portion and moves onto the photoreceptor 1. Since the transfer residual toner having the non-uniform polarity is recharged to the original negative electrode, the polarity of the charging roller 21 is the same as that of the charging roller 21, and the charging roller 21 is released from the electrostatic restraint (adhesive force). The scraping of the toner is also efficiently performed. As a result, continuous toner adhesion and long-term toner adhesion can be prevented.
[0065]
Further, the toner that has not been scraped off moves to the charging nip N according to the rotation of the charging roller 21, and is then discharged to the photoconductor 1 using the potential difference between the charging roller 21 and the photoconductor 1.
[0066]
In either case, the toner whose polarity has been controlled passes through the nip portion N of the charging roller 21. However, in the present invention, after the toner polarity is controlled to the photoconductor charging polarity, that is, the same polarity as the charging roller 21, Since the toner passes through the charging nip N, electrostatic adhesion of the toner to the charging roller 21 is prevented, and accumulation of the toner on the charging roller is also prevented.
[0067]
In the charging nip portion N, the toner polarity is more uniformly controlled by the charging roller 21 that supplies the charges of the same polarity. The transfer residual toner having the polarity controlled moves to the developing section D according to the rotation of the photoconductor, is collected by the developing device 4, and is reused.
[0068]
As described above, by releasing the electrostatic binding force using the charge control agent, the toner scraping property is dramatically improved as compared with the case where the toner attached to the charging roller 21 is physically scraped off by the scraping member 22. It is possible to prevent the charging roller from being stained for a long period of time, so that uniform charging is possible.As an effect, high image quality can be achieved even in a simultaneous development cleaning system that does not have a cleaner device to collect transfer residual toner. it can.
[0069]
Further, due to the dual action of the polarity control agent and the discharge near the charging nip, more efficient toner polarity control is performed.
[0070]
Since the polarity is controlled, the recovery by the developing unit is performed efficiently, so that a ghost image is prevented. In particular, high image quality is maintained for a long time even in a high-speed machine with a high process speed or under a sudden environmental change. .
[0071]
In Japanese Patent Application Laid-Open No. 06-149020, if the toner adhering to the charging roller is scraped off to the upstream portion of the photosensitive member, the toner re-adheres to the charging roller when the toner moves to the charging nip, and the charging roller cannot be cleaned. However, in the present invention, re-adhesion of the toner is prevented by controlling the polarity of the toner as described above.
[0072]
The toner scraping member 22 may be provided with a polarity control agent capable of controlling the polarity of the toner to the same polarity as the charging polarity of the photoconductor. This is more effective especially when a large amount of transfer residual toner is continuously generated.
[0073]
(2) Charging roller 21
The charging roller 21 serving as a charging member includes a core 21a and a conductive elastic layer 21b concentrically provided in a roller shape around the core, as shown in the layer configuration model diagram of FIG. And a surface layer 21c covering the outer peripheral surface of the elastic layer 21b (conductive rubber roller).
[0074]
For example, a raw material composed of EPDM, conductive carbon black, a vulcanizing agent, and an auxiliary agent is heated and melted by two rolls, and the resulting material is filled in a roller mold having a cored bar 21a, and vulcanized and molded to form an elastic material. After the layer 21b is formed, the surface is coated with a nylon resin coating material in which a conductive agent is dispersed on the order of several tens to several hundreds of micrometers to form the surface layer 21c.
[0075]
The surface layer 21c can have a multilayer structure as needed. A polarity control agent for controlling the polarity of the toner is applied to the surface layer 21c.
[0076]
Hereinafter, a material example of the charging roller 21 will be described.
[0077]
A: Material for forming elastic layer 21b
For example, synthetic rubbers such as EPDM, NBR, butyl rubber, acrylic rubber, urethane rubber, polybutadiene, butadiene styrene rubber, butadiene acrylonitrile rubber, polychloroprene, polyisoprene, chlorosulfonated polyethylene, polyisobutylene, isobutylene isoprene rubber, fluorine rubber, and silicone rubber And natural rubber.
[0078]
The elastic material may be in the form of a sponge foamed to an appropriate cell diameter using a foaming agent as needed.
[0079]
Further, the elastic material can be easily made conductive by the conductive filler. Examples of such conductive fillers include metal powders and fibers such as aluminum, nickel, stainless steel, palladium, zinc, iron, copper, and silver, zinc oxide, tin oxide, titanium oxide, copper sulfide, and zinc sulfide. And carbon powders such as acetylene black, Ketjen black, PAN-based carbon, and pitch-based carbon. These can be used alone or in combination of two or more.
[0080]
B: Material forming surface layer 21c
For example, acrylic resin, polyethylene resin, polyester resin, polyurethane resin, polysulfonic acid resin, epoxy resin, phenol resin, styrene resin, nylon resin, polyvinyl chloride, alkyd resin, silicone resin, urea resin, melamine resin, fluorine resin, etc. Resin, polybutadiene, butadiene styrene rubber, butadiene acrylonitrile rubber, polychloroprene, polyisoprene, chlorosulfonated polyethylene, polyisobutylene, isobutylene isoprene rubber, acrylic rubber, urethane rubber, polysulfide synthetic rubber, fluorine rubber, silicone rubber, etc. There are synthetic rubbers, not only these alone, but also those obtained by copolymerizing the constituents of these resins in monomer units, and furthermore, a polymer substance composed of a combination of urethane and acrylic It can be used in combination of two or more as.
[0081]
These surface layer resins may be dissolved or dispersed in an appropriate solvent and coated as a coating material, or may be coated with a tube made using an extruder or the like.
[0082]
C: Polarity controlling agent
In the present invention, the polarity control agent has a capability of controlling a toner, which is reversely charged to a polarity opposite to a charged polarity of an image carrier in a transfer step, to a charge having the same polarity as a developing toner.
[0083]
The polarity controlling agent can be applied by a method of dispersing and mixing on the surface layer 21c of the charging roller 21 or a method of coating the surface layer 21c by means such as dipping.
[0084]
Examples of such a polarity controlling agent include a coupling agent, a resin modified with the coupling agent, an ionic dye / pigment and an organometallic compound, a resin, and a modified silicone oil. Coupling agents with stable properties are preferred.
[0085]
The following are specific examples of substances.
[0086]
1) Coupling agent
Examples of the coupling agent include a silane-based coupling agent, a titanate-based coupling agent, and an aluminum-based coupling agent. Specific examples are shown below.
[0087]
▲ 1 ▼. Examples of the silane coupling agent include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, Bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethyldiethoxysilane , Dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1.3-divinyltetramethyldisilo Xanthane, 1.3-diphenyltetramethyldisiloxane, dimethylpolysiloxane having 2 to 12 siloxane units per molecule and having hydroxyl groups bonded to silicon atoms, each of which is located at one of the terminal units, one at a time Is mentioned.
[0088]
Further, aminopropyltrimethoxysilane having a nitrogen atom, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, monobutylamino Propyltrimethoxysilane, dioctylaminopropyldimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine, trimethoxysilyl-γ-propylpenzylamine And the like are also used alone or in combination.
[0089]
Among them, an amino silane coupling agent having a nitrogen atom and a silane coupling agent having a hydrophobic group composed of a linear hydrocarbon are preferable.
[0090]
▲ 2 ▼. Examples of the titanate-based coupling agent include isopropyl triisostearoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, tetra ( 2,2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, bis (dioctylpyrophosphate) oxyacetate titanate, bis (dioctylpyrophosphate) ethylene titanate, isopropyltrioctanoyl titanate, isopropyldimethacrylisostearoyl Titanate, isopropyl tridodecyl benzene sulfonyl titanate, isopropyl isostearyl diacryl Taneto, isopropyl tri (dioctyl phosphate) titanate, isopropyl tricumylphenyl titanate, tetraisopropyl bis (dioctyl phosphite) titanate, and the like.
[0091]
Among them, isopropyl triisostearoyl titanate having a hydrophobic group composed of a linear hydrocarbon is preferable.
[0092]
(3). Examples of the aluminum-based coupling agent include acetoalkoxyaluminum diisopropylate.
[0093]
2) Resin modified with coupling agent
Examples of such a resin include a silane-based coupling agent-modified silicone resin.
[0094]
Such a silane coupling agent is as described above, and among them, aminosilanes are preferable, and more specifically, for example, 3-aminopropyltrimethoxysilane, (N, N-dimethyl-3-aminopropyl) ) Trimethoxysilane, (N, N-diethyl-3-aminopropyl) trimethoxysilane, N-methylaminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-methacryloxypropyltri Methoxysilane and γ-glycidoxypropyltrimethoxysilane. Further, N- [3- (triethoxysilyl) propyl] -4,5-dihydroimidazole, trimethoxysilylpropyldiethylenetriamine and the like are also used.
[0095]
3) Ionic dyes and pigments and organometallic compounds
Examples of the ionic compound include nigrosine dyes, azine dyes, imidazole compounds such as imidazole metal salts and dimers, triphenylmethane dyes and pigments, quaternary ammonium salts, and polymers having quaternary ammonium salts as side chains.
[0096]
Further, a metal compound of an aromatic carboxylic acid derivative typified by a chromium compound or a zinc compound of di-tert-butylsalicylic acid, an aromatic urea compound typified by bifluorophenylurea, and the like can also be used.
[0097]
4) Resin
Acrylic resin, fluorine resin, silicone resin, and the like.
[0098]
5) Modified silicone oil
As such a silicone oil, one having a viscosity at 25 ° C. of 0.5 to 10000, preferably 1 to 1000 centistokes is used. For example, dimethyl silicone oil, -part of a methyl group is modified with an alkyl group. Examples include alkyl-modified silicone oil, methylphenyl silicone oil, methylstyrene-modified silicone oil, amino-modified silicone oil, fluorine-modified silicone oil, epoxy-modified silicone oil, alcohol-modified silicone oil, and polyether-modified silicone oil. Among them, an amino-modified silicone oil having a high polarity control effect is preferable.
[0099]
(3) Toner scraping member 22
Examples of the toner scraping member (cleaning member) 22 for scraping off deposits such as toner from the charging member 21 include a blade, a fur brush, and an elastic roller. Among them, the toner scraping member 22 has excellent contact property with the attached toner and excellent scraping property. bladeIs preferred. In the present invention, a blade-shaped toner scraping member is used.
[0100]
1) Blade
As an example, the blade member 22 as the toner scraping member can be manufactured by adhering a flat elastic layer formed by injection molding or press molding to a support layer made of a metal or a resin plate via an adhesive. it can.
[0101]
As shown in FIGS. 1 to 3, the arrangement of the blade member 22 is preferably such that the edge portion of the blade member 22 is opposed to the charging roller 21 and is brought into contact with the downstream side of the charging roller (blade facing contact). The downstream side is a charging downstream side, and means an arc on the left side of the drawing divided by a straight line D passing through the center A of the charging nip N and the center B of the charging roller 21 as shown in FIG. It is more preferable that the vertical straight line E is within the range between the point F where the straight line E contacts the downstream arc and the nip center A.In the present invention, this blade facing contact form is adopted.
[0102]
Also,As a reference example,As illustrated in FIG. 4, a method of contacting the inner surface of the blade (contacting the blade surface) and securing a nip width with the charging roller 21 may be used. In this case, the contact between the blade 22 and the charging roller 21 is improved as compared with the configuration of FIG.
[0103]
Materials constituting the blade, for example, silicone material, urethane material, nitrile butadiene rubber, modified products of each, further elastic bodies such as blended products, stainless steel, metals such as aluminum, plastic resins and the like, among which Silicone materials and urethane materials having elasticity and excellent toner releasability are preferred.
[0104]
As such a silicone material, a silicone rubber which is polymerized and cross-linked by a radical reaction, a condensation reaction, and an addition reaction and is preferably formed, specifically, a liquid silicone rubber, a heat-curable silicone rubber, and a low-temperature curing silicone rubber And so on.
[0105]
Urethane materials are urethane elastomers, liquid urethane rubbers, thermoplastic urethane rubbers, and the like, and urethane is generally obtained by reacting a curing agent with a prepolymer obtained by reacting an isocyanate with a polyester diol obtained from a dicarboxylic acid and a diol. be able to.
[0106]
Specifically, adipic acid and ethylene glycol are reacted to form a polyester diol, and further diphenylmethane diisocyanate is reacted to form a prepolymer. The urethane elastomer can be obtained by reacting butanediol and trimethylpropane.
[0107]
2) Fur brush
This section describes a fur brush type toner scraping member as a reference example.A fur brush used as a toner scraping member is a W-shaped weave or a V-shaped weave (also referred to as a U-shaped weave) made of filamentary fibers on a base fabric such as a woven fabric, a nonwoven fabric, a film, or a sheet. ) Means a brush shape woven by such a method.
[0108]
The fibers used for the fur brush include synthetic fibers, natural fibers, semi-synthetic fibers, and regenerated fibers.
[0109]
Specifically, first, as synthetic fibers, for example, nylon-6, nylon-66, nylon-12, nylon-46, polyamides such as aramid, polyesters such as PET, and polyolefins such as PE and PP , Polyvinyl alcohol, polyvinyl chloride and vinylidene, polyacrylonitrile, polyphenylene sulfide, polyurethane, polyfluoroethylene, carbon fiber, glass fiber and the like.
[0110]
Natural fibers include, for example, silk, cotton, wool, hemp, and the like.
[0111]
Semi-synthetic fibers include acetate and the like, and regenerated fibers include rayon and cupra.
[0112]
Further, composite fibers (split fibers and ultrafine fibers) obtained by compounding two or more kinds of synthetic fiber raw material components and melt-spinning them can be used.
[0113]
These fibers may be used alone or in combination of two or more.
[0114]
Further, the fur brush can have conductivity. For example, various fibers described above as conductive powders represented by metal powders such as iron, copper and silver, composite metal powders such as zinc oxide, tin oxide, titanium oxide and copper sulfide, and conductive carbon powders such as carbon black. Knead-type fibers mixed with materials and melt-spun, conductive fibers such as metal fibers and carbon fibers, and conductive fibers whose fiber surface is coated with a conductive polymer represented by an electron conjugated polymer such as polypyrrole and polyaniline And the like.
[0115]
As a method of contacting the fur brush with the charging roller, it is preferable to adjust the amount of penetration by the spacer. In order to adjust the effect of scraping the attached toner and controlling the polarity, besides adjusting the penetration amount, a method of increasing the fiber strength of the brush, a method of increasing the brush flocking density, a method of changing the brush flocking state (weaving method), Further, there is a method in which an elastic layer is provided as a base layer of the fur brush and pressed against the charging roller.
[0116]
Examples of the form of such a fur brush include a roller shape, a blade shape, a belt shape, and the like, and these may be used in a fixed state. Can be rotated in the forward direction and in the opposite direction.
[0117]
An example of the configuration of a roller-shaped fur brush will be described.
[0118]
The fur brush has thousands to hundreds of thousands of brushes / inch on a base cloth.²  It is obtained by winding a brush made of rayon fibers planted on a conductive substrate (core bar). Examples of the means for winding include a method of spirally winding a short width brush contact fabric around a cored bar, a method of laminating a wide brushed fabric corresponding to the circumferential length of the cored bar and the brush width, and the like. Can be
[0119]
Here, an elastic layer may be provided between the brush and the conductive substrate. The elastic layer material is EPDM, silicone rubber, urethane rubber, or the like, and may be made conductive by a conductive agent.
[0120]
(4) Toner
The toner used for developing the electrostatic latent image is not particularly limited, but a polymerized toner may be used from the standpoint of energy saving of the image forming apparatus and effective use of chemical products.
[0121]
The polymerized toner can be reduced in melting point (glass transition temperature) and spheroidized by a manufacturing method called direct polymerization, and has effects such as power saving in a fixing process, improvement of transfer efficiency, and prevention of adhesion to a photoreceptor. I have.
[0122]
However, on the other hand, in the cleaning means for scraping off the transfer residual toner on the photoreceptor and collecting the waste toner in the waste toner container, the toner passes through depending on the environmental conditions, and the ghost image and the charging are locally, but locally, nonuniform. It has been pointed out that there are cases.
[0123]
Therefore, such an occurrence can be prevented by combining with the image forming apparatus and the process cartridge of the present invention, so that high image quality can be obtained in any environment.
[0124]
The spherical state of the toner can be represented by an SF value, and from the viewpoint of improving transfer efficiency, SF-1 is preferably in the range of 100 to 140, and SF-2 is preferably in the range of 100 to 120. It is also preferable from the standpoint of properties and low melting point.
[0125]
Here, the measurement and calculation of the SF value will be exemplified.
[0126]
An electron microscope (FE-SEM, manufactured by Hitachi, Ltd.) randomly samples 100 toner particles of 2 μm or more that have been magnified 1000 times, and the image information is introduced into an image analyzer (Luzex III, manufactured by Nicolet) via an interface. The analysis was performed, and the calculation was performed using the following equations 1 and 2.
[0127]
Here, in the formula, MXLNG represents the absolute maximum length of the particle, PERIME represents the peripheral length of the particle, and AREA represents the projection surface of the particle. SF-1 indicates the degree of roundness of the particles, and SF-2 indicates the irregularities of the particles.
[0128]
(Equation 1)

[0129]
(Equation 2)

[0130]
Such a polymerized toner can be produced directly by subjecting the monomer composition to suspension polymerization. For example, first, a polymerizable monomer composition including a polymerizable monomer, a colorant, a polar resin, a release agent, a charge control agent, a polymerization initiator, a crosslinking agent, and the like is dispersed in an aqueous medium and polymerized. To form particles of the hydrophilic monomer composition. Then, a polar resin is localized on the surface of the particles, and the polymerizable monomer in the particles is polymerized to form toner particles as a binder resin. By adding a water-soluble polymerization initiator to an aqueous medium and treating the surface of the toner particles, it can be produced with a high yield.
[0131]
Hereinafter, main materials will be exemplified.
[0132]
As the polymerizable monomer, a styrene polymer, a styrene-acrylate copolymer, a styrene-methacrylate copolymer, a polar resin such as a polyester resin, a styrene copolymer, and the like, a coloring agent, carbon black, disazo-based As a release agent such as a yellow pigment, a quinacridone-based magenta pigment, a phthalocyanine-based cyan pigment, a paraffin wax, a polyolefin wax, a Fischer-Tropsch wax, a low-melting substance having an endothermic main peak value of 120 ° C. or less in a DSC endothermic curve, Amide wax, higher fatty acid, higher alcohol ester wax, etc., crosslinking agents such as divinylbenzene, carboxylate, divinylaniline, etc., and charge control agents such as nigrosine dye, triphenylmethane dye, etc. Acid compounds, urea derivatives, such as negatively charged, such as azo dyes, as the polymerization initiator, an azo or peroxide type polymerization initiators and the like.
[0133]
(5) Photoconductor 1
In the photoconductor 1 as an image carrier in this example, a charge injection layer can be provided on the surface of the photosensitive layer. As a result, the chargeability is improved, and at the time of image exposure, it plays a role of more efficiently releasing the charged charges to the conductive support, thereby reducing the residual potential. Image is obtained.
[0134]
Injection charging can be achieved by combining contact charging and an image carrier having a charge injection layer laminated thereon. Injection charging is a charging method in which a DC voltage is applied to a charging member so that the applied charge is efficiently held and formed on an image carrier (a member to be charged). It is a charging means that gives a minimum necessary charging potential as compared with a charging method using discharge, and is distinguished from DC charging, which is conventional DC voltage discharge charging.
[0135]
With this type of injection charging, fluctuations in chargeability due to environmental changes and changes in the thickness of the photoconductor can be suppressed to a smaller extent than conventional photoconductors without a charge injection layer, further improving image quality. At the same time, reduction of ozone due to discharge is realized.
[0136]
By the way, when the injection charging is performed, the discharge component is reduced. However, the transfer of the charge in the charging nip N is promoted, so that the effect of inverting the toner polarity is substantially maintained.
[0137]
Such charge injection layers include {1}. A resin layer in which an appropriate amount of light-transmitting and conductive particles are dispersed in an insulating binder resin, {2}. An inorganic layer made of a semiconductor or the like can be given, but an organic layer made of a conductive polymer can also be used.
[0138]
The charge injection layer will be specifically described.
[0139]
1) Resin layer composed of conductive particles and binder resin
Binder resins include polyester resin, polycarbonate resin, polystyrene resin, fluorine resin, cellulose, vinyl chloride resin, polyurethane resin, acrylic resin, epoxy resin, silicone resin, alkyd resin, vinyl chloride-vinyl acetate copolymer resin And the like.
[0140]
Examples of the conductive fine particles include metals such as copper, aluminum, silver, and nickel; zinc oxide, tin oxide, antimony oxide, tin oxide, and titanium oxide; and metal oxides such as solid solutions or fused materials thereof, polyacetylene, and polythiophene. And a conductive polymer such as polypyrrole, etc., but it is more preferable to select and use a metal oxide such as tin oxide having high transparency from the viewpoint of the translucency of the photoreceptor.
[0141]
The particle size of these conductive fine particles is preferably 0.3 μm or less, and most preferably 0.1 μm or less from the viewpoint of light transmission. When it is contained in the charge injection layer, the content of the conductive fine particles depends on the particle size, but is preferably in the range of 2 to 280% by weight based on the binder resin. If the content is less than 2% by weight, it is difficult to adjust the resistance of the charge injection layer, and if it exceeds 280% by weight, the coating properties of the binder resin may be partially reduced. Therefore, the content of the conductive fine particles is preferably in the range of 2 to 280% by weight based on the binder resin.
[0142]
Various additives can be added for the purpose of improving the dispersibility of the conductive fine particles, the adhesion to the binder resin, or the smoothness of the coating film after film formation. As for the improvement of dispersibility, it is very effective to modify the surface of the conductive fine particles with a coupling agent or a leveling agent. Further, from the viewpoint of improving the dispersibility, it is effective to use a curable resin as the binder resin.
[0143]
When a curable resin is used for the charge injection layer, a coating liquid in which conductive fine particles are dispersed in a solution of a curable monomer or oligomer is applied to the photosensitive layer, and after coating, the coating film is heated or irradiated with light. Is cured to form a surface layer. Examples of such a curable resin include, but are not limited to, acrylic resin, epoxy resin, phenol resin, melamine resin, etc. Any resin that causes a reaction and cures can be used.
[0144]
The charge injection layer is obtained by applying and drying a suitable solution or a dispersion solution of a binder resin, conductive fine particles, and additives as needed on a photoreceptor. 0.1 to 10 μm, optimally 0.5 to 5 μm.
[0145]
Here, the charge injection layer may contain a lubricant powder. The friction between the photosensitive member and the charging member or the friction between the photosensitive member and the cleaning member is reduced, and the dynamic load on the electrophotographic apparatus can be reduced. Further, since the releasability of the photoreceptor surface is improved, the adhesion of the developer can be prevented. As such lubricant particles, it is preferable to use a fluororesin, a silicone resin, or a polyolefin resin having a low critical surface tension.
[0146]
Particularly preferred is a tetrafluoroethylene resin. In this case, the amount of the lubricant powder is preferably 2 to 50% by weight, more preferably 5 to 40% by weight, based on the charge injection layer overlap. If the amount is less than 2% by weight, the effect of improving the chargeability may not be sufficiently exerted because the amount of the lubricant powder is not sufficient. Tend to.
[0147]
2) Charge injection layer made of inorganic material
For example, a semiconductor such as amorphous silicon can be used.
[0148]
The photoconductor made of semiconductor silicon can be manufactured continuously by using a plasma chemical vapor deposition apparatus by high-frequency glow discharge decomposition by selecting photoconductive amorphous silicon for the lower photosensitive layer.
[0149]
Examples of the charge injection layer made of a conductive polymer include electron conjugated polymers such as polypyrrole, polythiophene, and polyaniline, and organic polysilanes.
[0150]
The volume resistance value of the charge injection layer is 1 × 10⁸  Ωcm-1 × 10^FifteenIt is preferable to adjust it to the range of Ωcm.
[0151]
The volume resistivity of the charge injection layer is 1 × 10⁸  When the resistance is smaller than Ωcm, the electrostatic latent image cannot be held and image deletion occurs, and 1 × 10^FifteenIf it exceeds Ωcm, the charge cannot be sufficiently received from the charging member, and poor charging may occur.
[0152]
Therefore, the charge injection layer has a volume resistance of 1 × 10 5 in order to satisfy sufficient chargeability and image reproducibility.⁸  Ωcm-1 × 10^FifteenIt is preferable to prepare this in the range of Ωcm.
[0153]
The volume resistance of the charge injection layer was determined by preparing a charge injection layer on polyethylene terephthalate (PET) with a conductive film deposited on the surface, and using a volume resistance measurement device (4140B pAMATOR manufactured by Hewlett Packard) at 23 ° C. and 65 ° % In a 100% environment.
[0154]
(6) Example of manufacturing charging roller 21
[Production Example 1 of Charging Roller]
EPDM 100 parts by weight
4 parts by weight zinc oxide
Acetylene black 10 parts by weight
10 parts by weight of paraffin oil
1 part by weight of sulfur
The main component was kneaded with a twin-screw extruder while being cooled with water together with a vulcanization accelerator and a higher fatty acid. This was vulcanized and molded in a mold to produce an elastic roller having an outer diameter of 12 mm (core bar 6 mm).
[0155]
Next, the elastic roller was immersed and coated in a methylolated nylon solution dissolved in a methanol / toluene mixed solvent, and dried by heating at 120 ° C. for 1 hour.
[0156]
Roller resistance is 3 × 10⁶  It was. This is referred to as “charging roller 1”.
[0157]
[Production Example 2 of Charging Roller]
In Production Example 1 of the charging roller, the elastic body was foamed (average foam cell diameter: 100 μm) using a foaming agent (azodicarbodiamide), and the surface was polished to a diameter of 12 mm to form a foam roller.
[0158]
Next, a conductive tin oxide slurry (antimony-doped type) was dispersed in a urethane-acryl dispersion, and a viscous dispersion was prepared while increasing the viscosity with an acrylic resin. This solution was applied to the surface of the foam roller by a dipping method, preliminarily dried (50 ° C.), and finally heated and dried at 120 ° C. for 1 hour.
[0159]
This is referred to as “charging roller 2”.
[0160]
[Production Example 3 of Charging Roller]
Using a crosshead extruder, a conductive seamless tube having an inner diameter of 11.5 mm and a thickness of 250 μm was prepared from a resin composed of a sterene-ethylene-olefin copolymer and conductive carbon black.
[0161]
Next, the foamed roller of Production Example 2 of the charging roller was covered while blowing air.
[0162]
This is referred to as “charging roller 3”.
[0163]
[Production Example 4 of Charging Roller]
An aminosilane coupling agent (3-aminopropyltriethoxysilane) diluted to 1% by weight with toluene is impregnated and applied to the “charging roller 1”, dried at 80 ° C. for 1 hour, and then cured at 120 ° C. for 1 hour. did.
[0164]
This coupling agent-treated product is referred to as “charging roller 4”.
[0165]
[Production Example 5 of Charging Roller]
The “charging roller 2” was impregnated with a titanium coupling agent (isopropyl triisostearoyl titanate) diluted to 1% by weight with toluene, dried at 100 ° C. for 1 hour, and then cured at 150 ° C. for 1 hour.
[0166]
This treated coupling agent is referred to as “charging roller 5”.
[0167]
[Production Example 6 of Charging Roller]
A silane coupling agent (dodecyltriethoxysilane) diluted to 1% by weight with MEK was spray-coated on the “charging roller 3”, dried at 80 ° C. for 1 hour, and then cured at 120 ° C. for 1 hour.
[0168]
This coupling agent-treated product is referred to as “charging roller 6”.
[0169]
(7) As a toner scraping member (cleaning member) 22
Examples of manufacturing blades and fur brushes
[Production Example 1 of Blade]
The two-component silicone rubber was cured at 150 ° C. to form a sheet, and then cured at 200 ° C. to obtain a molded silicone rubber having a thickness of 3 mm. This molded body was cut into a length of 15 mm and a width of 230 mm, and bonded to a 0.1 mm-thick stainless steel substrate so that 10 mm of the length was fixed, to produce a blade.
[0170]
This is referred to as “blade 1”.
[0171]
[Production Example 2 of Blade]
A high-temperature-curable silicone rubber (liquid silicone rubber) was injection-molded on a primer-treated 0.07 mm-thick stainless steel substrate to form a 0.7-mm silicone rubber elastic layer, and then vulcanized at 200 ° C. This integrally molded body was cut to produce a blade.
[0172]
This is referred to as “blade 2”.
[0173]
[Production Example 3 of Blade]
MDI (4,4'diphenylmethane diisocyanate), a urethane raw material mainly composed of a polyester diol composed of ethylene glycol and adipic acid were reacted in a nitrogen atmosphere to synthesize a prepolymer having a polyester average molecular weight of 1700.
[0174]
A curing agent was added to the mixture, and the mixture was poured into a molding die, cured at 150 ° C., demolded, heated and cured, and cut in the same manner as “Blade 1” to prepare a blade.
[0175]
This is referred to as “blade 3”.
[0176]
[Production Example 4 of Blade]
A Ti-based coupling agent (isopropyl triisostearoyl titanate) was diluted with toluene to 1% by weight. This solution was impregnated with "Blade 1", taken out, heated and dried at 80 ° C, and further cured at 150 ° C for 1 hour.
[0177]
This is referred to as “blade 4”.
[0178]
[Production Example 5 of Blade]
The aminosilane coupling agent (3-aminopropyltriethoxysilane) was diluted with MEK to 1% by weight. This solution was impregnated with "Blade 3" to perform a coupling treatment.
[0179]
This is referred to as “blade 5”.
[0180]
[Production example 1 of fur brush](Reference example)
Rayon fiber (average fiber diameter: 15 μm) kneaded with conductive carbon is woven in a W shape with respect to the base cloth, and the fiber density is 200,000 fibers / inch.^Two And a brush fabric having a pile length of 5 mm was produced. This was spirally wound around a stainless steel core having a diameter of 6 mm via an adhesive to produce a roller-shaped fur brush.
[0181]
This is referred to as "fur brush 1".
[0182]
[Production example 2 of fur brush](Reference example)
Weave PET fibers with an average fiber diameter of 13 μm in a W shape with respect to the base cloth, and have a fiber density of 200,000 fibers / inch.^Two And a brush fabric having a pile length of 5 mm and a width of 10 mm.
[0183]
The brush fabric was impregnated by spraying a solution containing a 1% by weight of a Ti-based coupling agent (isopropyl triisostearoyl titanate) diluted with toluene and impregnated with the solution, and finally cured at 120 ° C for 1 hour.
[0184]
Next, a roller-shaped fur brush was wound in a spiral shape around an SUS core with an adhesive therebetween.
[0185]
This is referred to as "fur brush 2".
[0186]
(8) Example of manufacturing toner and developer
[Production Example 1 of Toner]
100 parts by mass of polyester resin
Metal azo dye 2.5 parts by mass
Low molecular weight polypropylene 4 parts by mass
4 parts by mass of carbon black
After the above materials were dry-mixed, they were kneaded with a twin-screw kneading extruder set at 150 ° C. The obtained kneaded material was air-cooled, finely pulverized by an air-flow type pulverizer, and then subjected to air classification to obtain a toner composition having a controlled particle size distribution.
[0187]
To this toner composition, 1.5% by weight of hydrophobically treated titanium oxide was externally added to prepare a toner having a weight average particle size of 7.0 μm.
[0188]
[Toner Production Example 2]
90 parts by mass of stellene
10 parts by mass of n-butyl acrylate
5 parts by mass of low molecular weight polypropylene
5 parts by mass of carbon black
2 parts by mass of metal-containing azo dye
Azo initiator 5 parts by mass
The above solution was added to 500 parts by mass of pure water in which 5 parts by mass of calcium phosphate had been dispersed, and dispersed by a homomixer. Finally, the polymer obtained by polymerizing at 75 ° C. for 10 hours was filtered and washed. After that, drying classification was performed to obtain a toner composition.
[0189]
2% by weight of hydrophobically treated titanium oxide was externally added to the toner composition to prepare a toner having a weight average diameter of 6.1 μm.
[0190]
The obtained toner is formed by a polymerization method, and shows a spherical shape when observed with an electron microscope. The shape factors were 120 for SF-1 and 110 for SF-2.
[0191]
[Developer Production Example 1]
7 parts by mass of the toner of Toner Production Example 1 was mixed with a developing carrier (100 parts by mass) obtained by coating a silicone resin on nickel zinc ferrite having an average diameter of 60 μm.
[0192]
This is referred to as “Developer 1”.
[0193]
[Developer Production Example 2]
7 parts by mass of the toner of Toner Production Example 2 was mixed with a developing carrier (100 parts by mass) in which an acryl-modified silicone resin was coated on nickel zinc ferrite having an average diameter of 60 μm.
[0194]
This is designated as “Developer 2”.
[0195]
(9) Production example of photoreceptor
[Production Example 1 of Photoconductor]
A photosensitive layer was laminated on an aluminum cylinder having a diameter of 30 mm to produce an OPC photosensitive member 1.
[0196]
The laminated layers are the following first to fourth layers in order from the aluminum cylinder.
[0197]
The first layer is an undercoat layer. A thin 30 μm-thick layer having conductivity was provided to smooth the defects of the aluminum cylinder and to prevent the occurrence of moire due to the reflection of laser exposure.
[0198]
The second layer is a positive charge injection preventing layer. In order to prevent the positive charge injected from the aluminum cylinder side from canceling the negative charge charged on the photoreceptor surface, 10⁶  A layer composed of an amylan resin and methoxymethylated nylon having a resistance adjusted to the order of Ωcm was formed to a thickness of about 1 μm.
[0199]
The third layer is a charge generation layer. A resin layer having a thickness of about 0.4 μm in which a disazo pigment is dispersed and capable of generating positive and negative charge pairs by laser exposure.
[0200]
The fourth layer is a charge transport layer. Hydrazone was dispersed in a polycarbonate resin to form a P-type semiconductor layer (about 25 μm). This layer has a function of transporting a positive charge generated in the charge generation layer to the surface of the photoreceptor, and a negative charge charged on the surface of the photoreceptor cannot move through this layer.
[0201]
This is designated as "Photoconductor 1".
[0202]
[Photoconductor Production Example 2]
In the photoconductor production example 1, a charge injection layer was provided as a fifth layer on the surface of the [photoconductor 1].
[0203]
The charge injection layer is a conductive resin layer in which tin oxide is dispersed in a photocurable acrylic resin.
[0204]
The tin oxide used was ultrafine particles having a particle size of about 0.03 μm, which was made conductive by doping with antimony, and was dispersed at 130% by weight with respect to the photocurable acrylic resin as the binder resin. Resistance is 4 × 10^ThirteenΩcm.
[0205]
In the charge injection layer, 30% by weight of tetrafluoroethylene resin particles were dispersed for the purpose of improving the surface slipperiness.
[0206]
This is designated as "Photoconductor 2".
[0207]
[Production Example 3 of Photoconductor]
An amorphous silicon photoreceptor comprising a blocking layer, a photoconductive layer, and a surface layer was prepared by using a glow discharge method on a mirror-finished aluminum cylinder having a diameter of 30 mm.
[0208]
First, the reaction chamber is about 5 × 10^-3After evacuating to Pa, various gases (SiH₄  , B₂  H₆  , NO, H₂  ) Was fed into the reaction chamber in a flow manner, and when the internal pressure reached about 20 Pa, glow discharge was caused to form a blocking layer of about 4 μm.
[0209]
Next, in the same manner,₄  , H₂  Using a gas, a 25 μm photoconductive layer was formed under an internal pressure condition of about 50 Pa.
[0210]
Furthermore, SiH₄  , CH₄  , H₂  Using a gas, glow discharge was performed under an internal pressure condition of about 60 Pa to form a surface layer made of Si and C with a film thickness of 0.4 μm, thereby producing an amorphous silicon photoreceptor.
[0211]
This is referred to as "Photoconductor 3".
[0212]
(10) Examples and comparative examples
Hereinafter, the effects of the present invention will be described with reference to Examples and Comparative Examples.
[0213]
First, a digital copier (GP55, manufactured by Canon Inc.) using a laser beam was modified and used as an image forming apparatus for evaluation.
[0214]
The GP55 is basically a digital copying machine of a reversal development system with a process speed of 150 mm / s, which includes a corona charging, a one-component jumping development, a corona charging, a blade-type cleaning container, and an exposure unit. It was modified to make a cleanerless examination machine as shown in FIG.
[0215]
1) Development: A two-component developing device (reversal development) 4 was made available. The bias weighed a square wave of -500 V / 1000 Vpp (3 kHz).
[0216]
2) Charging: A contact charging device 2 using a charging roller 21 as a charging member, and a cleaning member (toner scraping member) 22 was brought into contact with the charging roller 21. An external drive motor was connected to the charging roller 21 so as to be able to rotate opposite to the photoconductor 1, and the peripheral speed difference was set to 110%. Further, an external drive is provided for the roller-type cleaning member so that the cleaning member rotates counter to the charging roller.
[0217]
3) Charging bias
: -1300 V for DC charging, -700 V / 1500 Vpp (800 Hz) for AC charging, and weak DC voltage (-1000 V) for injection charging were applied by an external power supply.
[0218]
4) Cleaning container: The cleaning blade and the waste toner container were removed to remove the cleaner.
[0219]
Next, in the evaluation, a 6% character original was subjected to continuous image output for 10k sheets by A4 landscape feed, and image fog caused by ghost and poor charging was measured with a reflection densitometer. The durable environment is 23 ° C./relative humidity 60% (N / N environment), 23 ° C./relative humidity 10% (N / L environment), and 15 ° C./relative humidity 10% (L / L environment).
[0220]
In this evaluation, the difference (%) before and after the image was displayed was calculated using a reflection densitometer (TC-6MC, Tokyo Denshoku Technical Center) based on JIS Z8722 (0-45 degree method), and the fog density was determined.
[0221]
The evaluation levels are as shown in Table 1. When the image quality is less than 5%, it is judged that there is no practical problem.
[0222]
[Example 1]
The above-mentioned digital copying machine is equipped with a contact charging device in which the "blade 1" is abutted against the "charging roller 6" which has been surface-treated with a coupling agent. In this case, image endurance of 10k sheets was performed by DC charging, and fog before and after the endurance was evaluated.
[0223]
Here, the developer used was "developer 2" composed of a polymerized toner, and the photoreceptor used was "photoreceptor 2" having a charge injection layer.
[0224]
Table 2 summarizes the results based on the evaluation levels in Table 1.
[0225]
In the present embodiment, the transfer residual toner was favorably collected by the coupling agent treatment, and the fog was 1% or less even in a severely charged L / L environment. As a result, high image quality was achieved.
[0226]
[Examples 2 to 4]
The same evaluation as in Example 1 was performed using each member shown in Table 2.
[0227]
Here, with respect to the rotation of the charging roller, the “blade 4” was opposed to contact, and the “fur brush 1” and “fur brush 2” were opposed to rotate at the same peripheral speed.Examples 3 and 4 using “Fur brush 1” and “Fur brush 2” are reference examples.
[0228]
As a result, by using a fur brush whose surface has been treated with a coupling agent as a cleaning member (toner scraping member) 22 of the charging roller 21 (Examples 3 and 4), good image quality can be obtained. In Example 2, as in Example 1, good image quality of 1% or less fog was obtained even in an L / L environment.
[0229]
[Examples 5 to 7]
When the same evaluation as in Example 1 was performed using each member shown in Table 2, good image quality of 1% or less fog was obtained under each charging condition. Here, the alternating current component of Example 6 was set to 1.1 kVpp and 1.0 kHz.
[0230]
Example 8
The same evaluation as in Example 1 was performed in a state where the “blade 5” surface-treated with the coupling agent was brought into surface contact with the charging roller 21 as shown in FIG. 4 to secure a nip having a width of about 1 mm.Example 8 is also a reference example.
[0231]
As a result, the same level of high image quality as in Example 1 was obtained.
[0232]
[Examples 9 to 11]
The same evaluation as in Example 1 was performed in two environments of N / N and N / L using each member shown in Table 2.Example 10 using “Fur brush 1” is a reference example.
[0233]
As a result, sufficient image quality was obtained even in an N / L environment.
[0234]
[Examples 12 to 15]
Using the coupling member shown in Table 2 and “Photoconductor 1”, the same evaluation as in Example 1 was performed in two environments of N / N and N / L.Examples 14 and 15 using "Fur brush 1" and "Fur brush 2" are reference examples.
[0235]
Here, “Blade 1” and “Blade 4” were opposed to each other, and “Fur brush 1” and “Fur brush 2” were rotated oppositely.
[0236]
As a result, high image quality was achieved in the N / N environment, and in Examples 12 and 13 using the blade, good image quality was obtained with fog suppressed to 1 to 3% even in the N / L environment. .
[0237]
[Example 16]
When "blade 2" was abutted against "charging roller 4" (Table 2) and durability in an N / N environment by AC charging was performed, a high image quality of 1% or less fog was obtained.
[0238]
[Examples 17 and 18]
Using each member shown in Table 2, image endurance was performed in an N / N environment in the same manner as in Example 1. As a result, a good image in which fog was suppressed to 1 to 3% was obtained.Example 18 using "Fur brush 1" is a reference example.
[0239]
[Examples 19 to 25]
Using the members shown in Table 2, image durability was performed in an N / N environment in the same manner as in Example 1.Example 19 using "Fur brush 1" and "Fur brush 2" is a reference example.
[0240]
As a result, in the system in which the pulverized toner and the “photoconductor 1” are combined (Examples 24 and 25), the fog is at a level of 3% to 5% that is practically no problem, and further, the cleaning member (toner scraping member) By performing the coupling treatment (Examples 19 to 23), the fog was reduced to 2%, and the image was improved.
[0241]
[Comparative Example 1]
“Charging roller 1” was brought into contact with “photoconductor 1”, and the same evaluation as in Example 1 was performed in an N / N environment using “developer 1”. The charging roller was driven to rotate by the photoconductor, and the charging was DC charging.
[0242]
As a result, fogging occurred from the early stage of durability, and image quality deteriorated.
[0243]
[Comparative Example 2]
The same evaluation as in Example 1 was performed in an N / N environment using “Fur Brush 1”. The charging member was rotated externally (peripheral speed difference 130%) by external driving. Here, the "fur brush 1" has confirmed that the initial charge potential required for image formation can be obtained by the idling evaluation.
[0244]
As a result, fogging occurred from the early stage of durability, and image quality deteriorated.
[0245]
[Comparative Example 3]
When the same evaluation was performed by the AC charging in Comparative Example 1, fog was generated from the early stage of durability, and the image quality was deteriorated.
[0246]
[Table 1]

[0247]
[Table 2]

[0248]
(11) Other
1) In the present invention, the image forming apparatus may be provided with a cleaner device for collecting the transfer residual toner on the image carrier. In this case, it is preferable to install the cleaner device between the transfer unit 5 and the charging unit 2. The cleaner device may be provided in a process cartridge.
[0249]
2)The charging roller 21 as a contact charging member isMaterials such as felt and cloth can also be used. These various materials can be combined and laminated to obtain more appropriate elasticity and conductivity.
[0250]
3) When an AC (alternating) voltage is superimposed on the charging bias or the developing bias, a waveform of the AC voltage, such as a sine wave, a rectangular wave, and a triangular wave, can be used as appropriate. Alternatively, a rectangular wave formed by periodically turning on / off a DC power supply may be used. As described above, a bias whose voltage value periodically changes can be used as the waveform of the AC voltage.
[0251]
4) The image exposing means for forming the electrostatic latent image is not limited to the laser scanning exposing means for forming a digital latent image as in the embodiment, but is a usual analog image exposing means. It may be. Exposure means such as a light emitting element array such as an LED or a combination of a light emitting light source such as a fluorescent lamp and a liquid crystal shutter array may be used, as long as an electrostatic latent image corresponding to image information can be formed.
[0252]
5) The image carrier may be an electrostatic recording dielectric or the like. In this case, after the dielectric surface is uniformly charged to a predetermined polarity and potential, the charge is selectively removed by a charge removing means such as a charge removing needle head or an electron gun to write and form a desired electrostatic latent image.
[0253]
6) Generally, the developing means of the electrostatic latent image is such that non-magnetic toner is coated on a developing member with a blade or the like, and magnetic toner is coated by a magnetic force and conveyed to be developed in a non-contact state with the image carrier. (One-component non-contact development), a method of developing the toner coated as described above in contact with the image carrier (one-component contact development), and mixing a magnetic carrier with the toner particles. Using the developer as a developer and transporting it by magnetic force to develop it in contact with the image carrier (two-component contact development), or developing the two-component developer in a non-contact state ( (Two-component non-contact development).
[0254]
The two-component contact developing method is often used from the viewpoints of high image quality and high stability. In addition, a one-component contact developing method or a two-component contact developing method in which a developer is brought into contact with an image carrier for development is effective in improving simultaneous toner recovery at the time of development, and is preferable.
[0255]
When a polymerized toner is used as the toner particles in the developer, a developing method such as a one-component non-contact developing method or a two-component non-contact developing method as well as the one-component contact developing method or the two-component contact developing method described above is used. , A sufficient recovery effect can be obtained.
[0256]
7) The transfer means is not limited to the transfer roller 5, but may be a belt transfer device, a transfer corona charger, or the like. Further, using an intermediate transfer member such as a transfer drum or a transfer belt, not only a single-color image can be formed but also a multi-color or full-color image can be formed by multiple transfer.
[0257]
【The invention's effect】
As described above, in the present invention, a rotating image carrier, a charging unit for charging a surface of the image carrier, a latent image forming unit for forming an electrostatic latent image on a charged surface of the image carrier, An image forming apparatus including developing means for developing an electrostatic latent image as a toner image, transfer means for transferring the toner image to a recording medium, and transfer residual toner in a process cartridge mounted on such an image forming apparatus By controlling the polarity, the toner is prevented from accumulating on the contact charging member of the charging means, and the toner collecting performance of the developing means is improved. As a result, uniform charging was maintained over a long period, and high image quality was achieved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment;
FIG. 2 is a schematic diagram of a layer configuration of a charging roller.
FIG. 3 is a view for explaining a procedure in which a blade as a toner scraping member is disposed so as to face and contact a charging roller
FIG. 4 is a diagram illustrating a state in which a blade as a toner scraping member is disposed in surface contact with a charging roller.
[Explanation of symbols]
1 Photoconductor
2 Contact charging device
21 Charging roller
22 As a toner scraping member (cleaning member) from the charging roller
Blade
3 latent image forming means (laser scanner)
4 Developing device
5 Transfer roller
6 Fixing device
P Transfer material (plain paper, etc.)
S1 to S3 bias application power supply

Claims (16)

Rotating image carrier, charging means for charging the surface of the image carrier, latent image forming means for forming an electrostatic latent image on the charged surface of the image carrier, and developing the electrostatic latent image as a toner image Developing means, and an image forming apparatus including a transfer means for transferring the toner image to a recording medium,
Said charging means is rotated in the reverse direction at the contact portion between the image bearing member to the image bearing member, a charging roller for charging the surface of the image bearing member voltage is applied, with respect to the charging roller A blade-shaped toner scraping member that scrapes toner on the charging roller onto the image carrier upstream of the contact portion with respect to the rotation direction of the image carrier with the edge portion in counter contact with at least the image carrier; The image forming apparatus according to claim 1, wherein the charging member has a polarity control agent for controlling the toner charge to have the same polarity as the charging polarity of the image carrier. 2. The image forming apparatus according to claim 1 , wherein the surface of the toner scraping member has a polarity control agent for controlling the toner charge to have the same polarity as the charge polarity of the image carrier. The image forming apparatus according to claim 1, wherein the toner is a spherical toner generated using a polymerization method. 4. The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor having a photosensitive layer on a conductive substrate. 5. The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor having at least a photosensitive layer and a charge injection layer on a conductive substrate. The image forming apparatus according to claim 5 , wherein the charge injection layer is a resin layer in which a metal oxide is dispersed. The image forming apparatus according to claim 5 , wherein the charge injection layer is an inorganic semiconductor layer. 8. The image forming apparatus according to claim 1 , wherein the developing unit also serves as a cleaning unit that collects a transfer residual toner remaining on the image carrier after transferring the toner image to a recording medium. Image forming apparatus. At least a rotating image carrier, and a charging unit for charging a surface of the image carrier, a process cartridge detachable from the image forming apparatus main body.
Said charging means is rotated in the reverse direction at the contact portion between the image bearing member to the image bearing member, a charging roller for charging the surface of the image bearing member voltage is applied, the edge with respect to the charging roller And a blade-like toner scraping member that scrapes toner on the charging roller onto the image carrier upstream of the contact portion with respect to the image carrier rotation direction with respect to the image carrier rotation direction. A process cartridge, wherein the charging member has a polarity control agent for controlling the toner charge to the same polarity as the charging polarity of the image carrier. The process cartridge according to claim 9 , further comprising a developing unit configured to develop the electrostatic latent image formed on the charged surface of the image carrier as a toner image. 11. The process cartridge according to claim 9 , wherein a surface of the toner scraping member has a polarity control agent for controlling toner charge to the same polarity as the charging polarity of the image carrier. The process cartridge according to any one of claims 9 to 11, wherein the toner is a spherical toner generated by using a polymerization method. 13. The process cartridge according to claim 9, wherein the image carrier is a photoconductor having at least a photosensitive layer on a conductive substrate. 14. The process cartridge according to claim 9, wherein the image carrier is a photosensitive member having at least a photosensitive layer and a charge injection layer on a conductive substrate. The process cartridge according to claim 14 , wherein the charge injection layer is a resin in which a metal oxide is dispersed. The process cartridge according to claim 14 , wherein the charge injection layer is an inorganic semiconductor.

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